1. Technical Field
The present invention relates to an apparatus for securing a connection between two medical structures implanted in the body of a patient, and more particularly, to a locking mechanism for locking an end of a catheter onto the connector tube of an implantable vascular access device.
2. Background Information
Vascular access systems are utilized in the medical field for the transmission of fluids between a reservoir in an implanted vascular access device, and a body vessel in the patient. The vascular access device is surgically implanted by a physician into the subcutaneous tissue of a patient. Frequently, the device is implanted in the clavicular area of the chest, although it may also be implanted in other areas having sufficient underlying bony structure to provide support for the device. A catheter extends between the connector tube of the vascular access device and the body vessel, such as a blood vessel, for establishing fluid communication therebetween. The fluid generally comprises a liquid medicament that is injected into a reservoir of the vascular access device for use in treating a medical condition of the patient. Alternatively, the fluid can comprise a body fluid that is collected in the reservoir of the vascular access device for withdrawal and analysis.
Typically, a vascular access device is implanted in a patient in situations in which it is expected that treatment of the patient with the medicament will continue for at least a period of several months. One of the most common uses of such devices is for cancer treatment, where a chemotherapeutic agent is injected into the reservoir, and transported therefrom through the catheter and vessel to a targeted body site.
A vascular access device typically includes a septum or similar penetrable closure through which the liquid medicament may be injected or otherwise transferred from the outside environment into the reservoir. When the device includes a septum, the septum generally comprises an elastomeric wall that covers all or a part of a surface of the device that is accessible to a needle. The septum is penetrated by the needle for injecting the medicament into the reservoir, or alternatively, for withdrawing blood or other body fluid from the reservoir.
A vascular access device is implanted into a pocket area of the subcutaneous tissue that has been deemed suitable for such use by the physician. The device is implanted in a manner such that the septum is readily accessible to the needle, so that the needle injection can be accomplished without undue complication and trauma to the patient. Once implanted, the device remains generally stationary in the pocket so that needle access to the device is not compromised. In many cases, the device is sutured or otherwise attached to available tissue in the body pocket to inhibit exceptional movement or shifting.
In a typical vascular access device, the connector tube of the implanted vascular access device is typically connected to a catheter by pushing the catheter over the connector tube. Thereafter, a rigid sleeve, typically fabricated from plastic or metal, is pushed over the catheter and the connector tube to maintain the catheter in position relative to the tube. This design has certain shortcomings. For example, during insertion of the sleeve over the catheter, the catheter is highly compressed between the minor diameter of the sleeve and the bead of the connector tube. The catheter then re-expands after the minor diameter has gone past the bead. The minor diameter creates a step which is employed to insure that the sleeve will not subsequently inadvertently withdraw from the connection. Since the only elasticity in this connection is in the compression of the catheter, the physician may have difficulty “feeling” that the connection has been properly effected. In addition, the high residual stresses created in the catheter render it susceptible to stress cracking over time. Further discussion of these deficiencies is provided in the description of the prior art designs illustrated in FIGS. 1 and 2 herein.
It would be desirable to provide a locking mechanism for a vascular access device that provides for secure attachment between the connector tube and the catheter, and that avoids the shortcomings of the prior art.